It should not be that difficult. It is only a substitution, or plugging in, problem. Nothing to analyze really. That is if you know the formula and constants to use.

The question is about linear thermal expansion of a length of steel.
In Physics we learned for this case that
"the change in length is proportinal to the change in temperature"
delta L ----> L*(delta T)
delta L = k*[L*(delta T)] -------(i)